Pyridine → 2-[(3S,4R)-4-acetylthio-3-methoxy-2-oxoazetidin-1-yl]-3-methylcrotonic acid 2,2,2-trichloroethyl ester

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Reaction Steps

A solution of 3.26 g of 2-[(3S,4R)-4-(benzthiazol-2-yldithio)-3-methoxy-2-oxoazetidin-1-yl]-3-methylcrotonic acid 2,2,2-trichloroethyl ester in 36.3 ml of acetic anhydride and 12.4 ml of acetic acid is cooled to -15° and 1.7 g of triphenylphosphine are added. After stirring under nitrogen at the same temperature for 75 minutes, 24.8 ml of pyridine are added to the mixture. After stirring for a further 3 hours at 0°, the reaction mixture is concentrated by evaporation under reduced pressure and the resulting residue is purified by chromatography over silica gel with toluene and toluene/ethyl acetate (19:1). IR spectrum (in methylene chloride): characteristic absorption bands at 3.40, 5.63, 5.77, 5.80, 6.13, 7.25, 7.35, 8.26, 9.0, 9.52 and 11.90μ.

Provenance & Evidence